Reference is now made to FIG. 1 which illustrates an implementation architecture for a first order digital infinite impulse response (IIR) filter 10. The sequence X of (input) signal values received at input 12 of filter 10 is processed by multipliers, adders and delays to produce a sequence Y of (output) signal values at output 14. A first multiplier 16 has an input coupled to receive the sequence X of signal values received at input 12 and an output which produces a weighted sequence X of signal values formed by multiplying the sequence X of signal values received at input 12 by a first coefficient (weight or gain parameter) W0. An adder 18 combines a feed forward path from the output of the first multiplier 16 with a feedback path. An output of the adder 18 produces the sequence Y of signal values at the output 14. The feedback path is formed by a delay block 20 coupled in series with a second multiplier 22. The delay block 20 has an input coupled to receive the sequence Y of signal values and output a delayed sequence Y of signal values. The second multiplier 22 has an input coupled to receive the delayed sequence Y of signal values and an output which produces a weighted delayed sequence Y of signal values formed by multiplying the delayed sequence Y of signal values at output 14 by a second coefficient (weight or gain parameter) W1. The adder 18 sums the weighted sequence X of signal values (output from the first multiplier 16 in the feed forward path) with the weighted delayed sequence Y of signal values (output from the second multiplier 22 in the feedback path) to produce the sequence Y of signal values at output 14.
The time-domain expression for the filter 10 representing the output in terms of the input is given by the following:Yn=Xn*W0+Yn−1*W1 
Where: the subscript n denotes a time index for the sequence of signal values.
The first and second coefficients W0 and W1 have fixed values satisfying the following relationship:W0+W1=a constant, for example equal to 1
Those skilled in the art understand that the response of the filter 10 is very dependent on the values of the first and second coefficients W0 and W1. For example, with a relatively larger first coefficient W0 and a relatively smaller second coefficient W1, i.e., W0>W1, the filter has a fast signal response time but a poor signal noise filtering characteristic (see, FIG. 2A which illustrates very little filtering of the noise in sequence X has been accomplished in the sequence Y but the filter does exhibit a fast response time at the data state change 100). Conversely, with a relatively larger second coefficient W1 and a relatively smaller first coefficient W0, i.e., W1 >W0, the filter has a slow signal response time but a good signal noise filtering characteristic (see, FIG. 2B which illustrates significant filtering of the noise in sequence X has been accomplished in the sequence Y at expense of a poor response time at the data state change 100). Because the filter weights through the first and second coefficients are fixed in filter 10, the designer must choose and be satisfied with a certain filter performance relationship between response time and filtering characteristic. This may lead to a compromised or sub-optimal filter design and operation.
Additionally, it is noted that the filter 10 configuration lacks the ability to enhance signal strength.
There accordingly exists a need in the art address the foregoing problems.